1. Field of the Invention
The present invention relates to heat transfer devices such as a refrigeration machine of the vapor compression and expansion cycle type. The field of application of the invention includes refrigeration, air conditioning, heat pumps, and similar heat transfer applications of vapor compression machines.
2. Description of the Prior Art
Evolution of compression cycle type refrigeration systems has lead to many improvements in operation. These improvements may render a system more suited to a specific application, or may cause the system to become more efficient. Specific applications of a particular refrigeration system may include general purpose cooling, reversal of operation or xe2x80x9cheat pumpxe2x80x9d operation, specific tasks such as ice making, and others. Various constructions have evolved to meet the application, efficiency, cost, and other requirements of a specific refrigeration system.
The prior art has suggested plural condensing circuits in a refrigeration system for accomplishment of diverse purposes. These purposes may include variation of capacity, staging, zoning, defrosting, liquid and gaseous phase control, maintaining equilibrium within a system, and still others.
Capacity variation typically occurs when heat is rejected to ambient air, which may vary significantly in its temperature. Thus, despite a constant load, appropriate heat exchange capacity with respect to the heat accepting medium must be varied. Capacity variation generally is illustrated in U.S. Pat. No. 1,790,237, issued to Jesse G. King on Jan. 27, 1931. Condensers are generally arranged in parallel, and are selectively activated by appropriate valves. In King""s scheme, a first condenser is constantly charged from the compressor, while a second condenser is selectively and variably charged through a valve. No valve is present to prevent charging of the first condenser once a maximal pressure is reached in that condenser. By contrast, each condenser line or conduit in the present invention has a valve for preventing further charging while another line or conduit is charging.
It is also possible that the actual cooling load may vary. In an example, a building having plural designated cooling zones may have plural condensers, with one condenser dedicated to each zone. Even when there is only one temperature control zone, the load within that zone may vary. For example, when a system having a singular cooling zone cools a building which is susceptible to significant variations in occupancy, the system may be called upon to reject more or less heat. In both examples, plural condensers may be arranged in parallel, and activated as required.
An example is seen in U.S. Pat. No. 3,430,453, issued to John P. Norton on Mar. 4, 1969. In this scheme, plural condenser conduits are progressively opened and closed in order to maintain constant the pressure of refrigerant delivered to the expansion valve of an evaporator. By contrast, in the present invention, plural condenser conduits operate at different pressures with respect to one another, even though discharging refrigerant to the same evaporator.
Some refrigeration systems reject heat progressively from compressed refrigerant. This may occur, for example, since a desired temperature difference may be beyond the reach of a single condenser, especially in cases wherein two different media are selectively employed to dissipate rejected heat in stages. Even where the same heat accepting medium is employed, plural condensers arranged in parallel may be utilized to balance pressure conditions, control refrigerant between liquid and gaseous phases, and otherwise maintain equilibrium within a closed refrigeration system.
In U.S. Pat. No. 3,368,364, issued to John P. Norton et al. on Feb. 13, 1968, a valve enables utilization of one or two condensers, for purposes of preventing pressure fluctuation and its detrimental consequences. The valving scheme is similar to that seen in King. Again, a particular condenser or condenser conduit is constantly being charged when the compressor operates, and unlike the present invention, cannot be isolated from compressor output.
A further example is seen in U.S. Pat. No. 3,481,152, issued to William M. Seeley on Dec. 2, 1969. Pressure responsive valves enable charging of plural condenser conduits. However, unlike the present invention, one particular condenser conduit is always charged when the compressor operates. Remaining condenser conduits are charged responsive to detection of differing condenser pressures. By contrast, in the present invention, all condenser conduits are subjected to equal treatment, although they rotate functions in a repeating cycle of sequential charging, and experience differing degrees of charging with refrigerant at any one moment in time.
Heat may be recovered for use after being concentrated within a condenser. In modern heat pumps, heat exchangers employed for condensing and evaporation swap functions depending upon whether the system is called upon to heat or to cool. An example of a heat recovery scheme is seen in U.S. Pat. No. 3,069,867, issued to Clarence L. Ringquist on Dec. 25, 1962. Compressed refrigerant is selectively condensed in one or both of two condensers disposed in parallel. This choice enables a relatively great amount of heat of condensation to be concentrated within one condenser, for recovery of that heat for heating. At other times, when recovery is not desired, utilization of both condensers enables relatively greater rejection of heat to the air or to another medium. In the Ringquist scheme, selection of valve position depends upon whether heating is demanded. There is no provision for causing an alternating cycle wherein both condensers are alternately charged, as found in the present invention.
U.S. Pat. No. 4,722,197, issued to Byron McEntire on Feb. 2, 1988, describes an energy reclamation scheme employing two parallel condensers. However, there is no alternating cycle nor apparatus for assuring the same in the McEntire device, unlike the apparatus of the present invention.
In U.S. Pat. No. 2,244,312, issued to Alwin B. Newton on Jun. 3, 1941, two parallel condensers are located one inside and one outside a building. This arrangement enables an air conditioning system to reject heat to the ambient under normal conditions, and to reject heat to a part of the building requiring heating under other circumstances. There is no provision for assuring automatic alternating use of system condensers, unlike the apparatus of the present invention.
In a further example of diverse purposes, as seen in U.S. Pat. No. 3,357,199, issued to James R. Harnish on Dec. 12, 1967, plural parallel condensers enable isolation of one condenser for drainage purposes while maintaining the refrigeration system operable. As with the Ringquist scheme, the Harnish scheme varies total condenser capacity by selectively idling one or more condensers. Unlike the present invention, there is no recycling control wherein all condenser circuits are always utilized when the compressor is operating.
In other examples of refrigeration systems having plural condensers, refrigerant may be diverted from a condenser which normally rejects waste heat to a heat exchanger employed for partial melting of ice within an ice making machine or for defrosting an evaporator coil. Unlike the present invention, there is no automatic recycling control feature which selects a particular condenser or condenser conduit based upon characteristics within that condenser or condenser conduit. Rather, defrosting schemes respond to demand for defrosting.
Progress in efficiency of energy consumption has influenced compressor design, pressure and temperature parameters, and other design aspects. However, none of the purposes discussed above nor efficiency considerations shows automatic sequential or rotating control of the valve arrangement characterizing the instant refrigeration system.
The present invention improves upon efficiency of vapor compression and expansion cycle type heat transfer devices such as refrigeration systems and machines. Many principles of operation and components are generally conventional, apart from certain novel improvements described herein.
Major components of the novel refrigeration system include a compressor, a condenser or heat rejecting heat exchanger served by plural condensing conduits conducting compressed refrigerant from the compressor, and an expansion chamber or heat exchanger for absorbing heat. The invention adds, in addition to the plural condensing conduits, a valve located between the output of the compressor and the plural condensing conduits, and a valve controller. The valve is arranged to distribute compressor output of compressed refrigerant among the condensing conduits such that each condensing conduit is charged individually, and all condensing conduits are charged in sequential fashion. While any one condensing conduit is being charged, remaining condensing conduits are isolated from compressor output. All condensing conduits communicate simultaneously through respective conventional evaporation orifices or equivalent conduits into the expansion or evaporation chamber of the heat absorbing heat exchanger.
A novel arrangement of valves directs compressed refrigerant from the compressor sequentially to each one, and only to that one, of the plural condensing conduits until the selected condensing conduit reaches a maximum charge and resultant pressure. Only one of the condensing conduits is being charged at any one time.
After a first condensing conduit is fully charged, the next condensing conduit to be charged is opened to the compressor output and the condensing conduit which has just been fully charged is closed to the compressor output by appropriate valves. If there are more than two condensing conduits, the remaining condensing conduits are also closed to the compressor output. After the second condensing conduit is fully charged, it is disconnected from output of the compressor, and a subsequent conduit is connected.
This pattern is repeated until the last available condensing conduit is charged. After the last condensing conduit is fully charged, the first condensing conduit is once again charged. This marks the beginning of a new cycle. At any one point in time after the first cycle is complete, each one of the various condensing conduits is charged with refrigerant to an extent different from that of the other condensing conduits. This is because condensed refrigerant immediately starts to escape from its condensing conduit into the expansion chamber immediately upon charging. Refrigerant pressure within each condensing conduit starts to decline from its peak value as soon as communication with the output of the compressor is closed by a valve.
When a new cycle begins, the first condensing conduit is once again connected to the compressor output. Immediately prior to reconnection, pressure within the first condensing conduit has diminished by expansion into the expansion chamber until the first condensing conduit is now the condensing conduit with the lowest internal pressure.
The advantage of this arrangement is that at the beginning of the charging period for each condensing conduit, refrigerant pressure is at the lowest value it will attain throughout operation. Hence, loading of the compressor is minimized at this point in time, and although increasing, will be not be maximized until the condensing conduit is once again fully charged. The average load imposed on the compressor is thus reduced from the peak load.
By contrast, in a conventional system, as soon as equilibrium of pressure within the condensing circuit is attained, the compressor is continuously subjected to maximal loading. That is, in a conventional system, the compressor is constantly or continuously forcing additional refrigerant into a condensing line which has attained and maintains its maximal internal pressure, hence subjecting the compressor to maximal backpressure, within minor variations.
It is well established practice to delay commencing operation of a refrigeration compressor immediately or shortly after operation has been halted. This delay period allows condenser pressure to diminish by spontaneous evaporation or expansion into the expansion chamber of compressed refrigerant contained within the condenser. Loading of the compressor when starting after a suitable delay is not objectionably burdensome since pressure prevailing within the condenser has abated.
However, the prior art has not appreciated the benefits of continuously operating the compressor when the condenser experiences less than peak pressure. The present invention periodically reproduces this condition by sequential charging the plurality of condensing conduits. In the present invention, the compressor is continuously operating, thereby avoiding reduction in power or rate of heat transfer when the compressor is idle, as it would be in prior art systems which have temporarily ceased compressor operation.
In summary, the present invention has apparatus for assuring rotating or sequential charging of plural condensing conduits while the compressor operates continuously in a refrigeration system. Interruption of sequential charging or of compressor operation is incidental, such as will periodically occur when demand for chilling is satisfied, and the entire system is shut down. But with the compressor of the refrigeration system continuously operating when demand is not yet satisfied, the load imposed upon the compressor will periodically be reduced as each newly depressurized condensing conduit is connected to the output of the compressor.
Accordingly, it is an object of the invention to reduce average loading imposed upon the compressor of a vapor compression type refrigeration system while maintaining continuous compressor operation.
It is another object of the invention to control sequential charging of condensing conduits responsive to each condensing conduit becoming fully charged in turn.
Still another object of the invention is to achieve periodic load reduction imposed on the compressor without discontinuing compressor operation.
An additional object of the invention is to utilize generally conventional components of a vapor compression type refrigeration system.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is fully effective in accomplishing its intended purposes.